The goal of the research is to investigate the functional visual effects of different visual system anomalies using noninvasive tests of function. Basic psychophysical tests, which have been extensively used to study the properties of the normal visual system, are chosen carefully for the clinical situation. These clinical tests allow one to specifically address different levels of response within the visual system. Our present battery of tests includes measurement of retinal photoreceptor function, outer-plexiform and inner-plexiform layer function, optic pathway function (i.e., pre- or post-optic nerve head), and visual cortex function. These "quantitative layer-by-layer perimetry" tests will enable the clinician or researcher to follow (across the various levels of visual processing and in selected visual field areas) the time course of progression, effectiveness of therapy and/or the natural remission of functional disruption. As part of the study of retinal photoreceptor function, we have special interest in the directional sensitivity of the retina, both from a basic and clinical point of view. In particular, we seek to understand mechanisms subserving photoreceptor alignment properties.